Asphalt shingles generally are composed of a support layer or substrate, traditionally a felted fibrous layer or a fiberglass or glass mat layer. The support layer is saturated and impregnated with a waterproofing agent, such as a bituminous composition such as a blown molten petroleum-based asphalt composition. Excess asphalt is removed by scraping, leaving a waterproof asphalt saturated substrate. Subsequently, the asphalt saturated substrate is coated on one or both sides and to a predetermined thickness with a molten bituminous coating that may contain a finely ground mineral stabilizer or other fillers. This coating is sometimes referred to as a “filled coating.”
While the filled coating is still in a plastic or molten state, ceramic-coated mineral granules, normally opaque to ultraviolet light, are dropped and pressed onto at least the weather exposed portions of the filled coating. The granules become embedded in and cover the filled coating. When exposed to sunlight on a roof, the granules act to protect the filled coating and the saturated substrate from ultraviolet rays or actinic effects of the sun, as well as providing a decorative aesthetic. Cellophane strips may be applied to be back surface of the web to prevent the self-seal adhesive of stacked shingles from sticking in a bundle. A thin layer of powdered mineral matter or fine sand also may be applied to the back surface in a process known as back dusting. The strips and back dusting material prevent individual shingles cut from a finished web from sticking together when stacked in bundles. Traditional prior art shingle webs can tend to be relatively inflexible during manufacturing. This, in turn, can lead to damage during the manufacturing process as webs of shingle material encounter machine line bend radiuses and other stresses along the line.
The application of a polymeric film to the back and/or front surfaces of an asphalt coated shingle web during manufacturing has previously been suggested. When applied to the back surface, such film can eliminate the need for back dusting since the film itself provides the desired non-stick properties. The film can provide additional advantages such as enhanced adhesion along the glue lines between courses of shingles due to the more uniform and dust free surface of the film compared to a traditional back dusting material. It may also be advantageous to apply films in areas that will become other regions of an asphalt shingle such as, for instance, in areas that will become the headlap portions of shingles. Even granule covered portions that will be exposed to the environment when shingles are installed may incorporate a polymeric film to provide greater protection from exposure to the elements as well as manufacturing efficiencies.
With regard to the application of films to webs of shingle material, the prior art suggests continuously withdrawing a sheet of film from a prefabricated roll and merging the film with a moving web of shingle material as the web and the film are conveyed in a downstream processing direction. However, certain problems are inherent in such a technique. For instance, in order for a film to be rolled onto a prefabricated roll for use, the film must be strong enough to resist tearing, folding, and other damage during the rolling process and during the process of applying the film to a web of shingle material. The thickness of the polymeric material has to be sufficient to meet these criteria. However, such thicknesses often are significantly greater than is necessary to provide the desired benefit to shingles. Accordingly, the volume of polymeric material and thus manufacturing costs are increased. Also, the sourcing, storage, and manipulation of large rolls of polymeric film add extra complication and cost. Further, just as with rolls of substrate, the rolls of film must be monitored during manufacturing and mechanisms must be provided to replace rolls as they become empty without having to stop the manufacturing line.
A need exists for a method of applying films and other coatings to a moving web of shingle material during the manufacturing process that addresses and resolves the above and other problems and shortcomings with prior art methods. It is to the provision of such a method, and of shingle products produced by the method, that the present invention is primarily directed.